The present invention relates to novel calcilytic compounds, pharmaceutical compositions containing these compounds and their use as calcium receptor antagonists.
In mammals, extracellular Ca2+ is under rigid homeostatic control and regulates various processes such as blood clotting, nerve and muscle excitability, and proper bone formation. Extracelluiar Ca2+ inhibits the secretion of parathyroid hormone (xe2x80x9cPTHxe2x80x9d) from parathyroid cells, inhibits bone resorption by osteoclasts, and stimulates secretion of calcitonin from C-cells. Calcium receptor proteins enable certain specialized cells to respond to changes in extracellular Ca2+ concentration.
PTH is the principal endocrine factor regulating Ca2+ homeostasis in the blood and extracellular fluids. PTH, by acting on bone and kidney cells, increases the level of Ca2+ in the blood. This increase in extracellular Ca2+ then acts as a negative feedback signal, depressing PTH secretion. The reciprocal relationship between extracellular Ca2+ and PTH secretion forms an important mechanism maintaining bodily Ca2+ homeostasis.
Extracellular Ca2+ acts directly on parathyroid cells to regulate PTH H secretion. The existence of a parathyroid cell surface protein which detects changes in extracellular Ca2+ has been confirmed. See Brown et al., Nature 366:574, 1993. In parathyroid cells, this protein, the calcium receptor, acts as a receptor for extracellular Ca2+, detects changes in the ion concentration of extracellular Ca2+, and initiates a functional cellular response, PTH secretion.
Extracellular Ca2+ influences various cell functions, reviewed in Nemeth et al., Cell Calcium 11:319, 1990. For example, extracellular Ca2+ plays a role in parafollicular (C-cells) and parathyroid cells. See Nemeth, Cell Calcium 11:323, 1990. The role of extracellular Ca2+ on bone osteoclasts has also been studied. See Zaidi, Bioscience Reports 10:493, 1990.
Various compounds are known to mimic the effects of extra-cellular Ca2+ on a calcium receptor molecule. Calcilytics are compounds able to inhibit calcium receptor activity, thereby causing a decrease in one or more calcium receptor activities evoked by extracellular Ca2+. Calcilytics are useful as lead molecules in the discovery, development, design, modification and/or construction of useful calcium modulators which are active at Ca2+ receptors. Such calcilytics are useful in the treatment of various disease states characterized by abnormal levels of one or more components, e.g., polypeptides such as hormones, enzymes or growth factors, the expression and/or secretion of which is regulated or affected by activity at one or more Ca2+ receptors. Target diseases or disorders for calcilytic compounds include diseases involving abnormal bone and mineral homeostasis.
Abnormal calcium homeostasis is characterized by one or more of the following activities: an abnormal increase or decrease in serum calcium; an abnormal increase or decrease in urinary excretion of calcium; an abnormal increase or decrease in bone calcium levels (for example, as assessed by bone mineral density measurements); an abnormal absorption of dietary calcium; an abnormal increase or decrease in the production and/or release of messengers which affect serum calcium levels such as PTH and calcitonin; and an abnormal change in the response elicited by messengers which affect serum calcium levels.
Thus, calcium receptor antagonists offer a unique approach towards the pharmacotherapy of diseases associated with abnormal bone or mineral homeostasis, such as hypoparathyroidism, osteosarcoma, periodontal disease, fracture healing, osteoarthritis, rheumatoid arthritis, Paget""s disease, humoral hypercalcemia associated with malignancy and fracture healing, and osteoporosis.
The present invention comprises novel calcium receptor antagonists represented by Formula (I) hereinbelow and their use as calcium receptor antagonists in the treatment of a variety of diseases associated with abnormal bone or mineral homeostasis, including but not limited to hypoparathyroidism, osteosarcoma, periodontal disease, fracture healing, osteoarthritis, rheumatoid arthritis, Paget""s disease, humoral hypercalcemia associated with malignancy and fracture healing, and osteoporosis.
The present invention further provides a method for antagonizing calcium receptors in an animal, including humans, which comprises administering to an animal in need thereof an effective amount of a compound of Formula (I), indicated hereinbelow.
The present invention further provides a method for increasing serum parathyroid levels in an animal, including humans, which comprises administering to an animal in need thereof an effective amount of a compound of Formula (I), indicated hereinbelow.
The compounds of the present invention are selected from Formula (I) hereinbelow: 
wherein:
Y1 is a covalent bond, alkylene or alkenylene of up to 4 carbon atoms, unsubstituted or substituted by C1-4 alkyl, or O;
Y2 is methylene, unsubstituted or substituted by C1-4 alkyl or haloalkyl;
Y3 is covalent bond or O, S, Nxe2x80x94RIV or C1-4 alkylene-O, C1-4 alkylene-S, C1-4 alkylene-Nxe2x80x94RIV;
R3 and R4 are, independently, methyl or ethyl, or, together, form cyclopropyl;
R5 is aryl or fused aryl, dihydro or tetrahydro fused aryl, unsubstituted or substituted with any substituents being selected from the group consisting of OH, halogen, C1-4 alkyl, C1-4 alkoxy, C3-6 cycloalkyl, OSO2RIV, CN, NO2, OCF3, CF3, CH2CF3, (CH2)n CO2RIV, and Oxe2x80x94(CH2)n CO2RIV, wherein n is an integer from 0 to 3 and RIV is selected from the group consisting of H, C1-4 alkyl, C3-6 cycloalkyl;
or R5 is heteroaryl or fused heteroaryl; wherein the hetero-ring contains N, O or S, and is aromatic, dihydro or tetrahydro, unsubstituted or substituted with any substituents being selected from the group consisting of OH, OCH3, CH(CH3)2, halogen, C1-4 alkyl, C1-4 alkoxy, C3-6 cycloalkyl, OSO2RIV, CN, NO2, OCF3, CF3, CH2CF3, (CH2)n CO2H, (CH2)n CO2RIV, and Oxe2x80x94(CH2)n CO2RIV;
G is a covalent bond, CHR6 or Cxe2x80x94R6 wherein R6 is H, OH or O (forming a ketone);
R7 is H, OH, or Oxe2x80x94C1-4 alkyl;
R8 is H or C1-4 alkyl; or R7 and R8 together form a ketone;
A and B are, independently, selected from the group consisting of a bond, CH2, NH, O, S and Cxe2x95x90O, provided that either A or B is selected from CH2 and NH; or A and B together form a bond; or the A-B moiety is represented by CHxe2x95x90CH or Cxe2x89xa1C; wherein
X1 and X5 are independently selected from the group consisting of H, halogen, CN, NO2, C1-4 alkyl, cycloalkyl, CH2-aryl, and CH2-heteroaryl; provided that either X1 or X5 is H; X2, X3 and X4 are selected from the group consisting of H, halogen, Oxe2x80x94C1-4 alkyl, O-aryl, O-heteroaryl, CH2-aryl. CH2-heteroaryl, alkyl, C(O)aryl, C(O)heteroaryl, CH(OH)aryl, CH(OH)heteroaryl; and Jxe2x80x94K;
J is a covalent bond, alkylene, O-alkylene or alkenylene of up to 5 carbon atoms, unsubstituted or substituted by a substituent selected from the group consisting of C1-4 alkyl, OH, O(forming a ketone), aryl, heteroaryl, and NRxe2x80x2Rxe2x80x3, wherein Rxe2x80x2 and Rxe2x80x3 are independently selected from the group consisting of H, alkyl, aryl, heteroaryl, C(O)alkyl, C(O)aryl, and C(O)heteroaryl;
K is selected from the group consisting of, CO2RIV, OH, and CN;
and pharmaceutically acceptable salts and complexes thereof.
Preferably, the compounds of the present invention have a structure according to Formula (II): 
wherein:
R3 and R4 are, independently, methyl or ethyl, or, together, form cyclopropyl;
R5 is aryl or fused aryl, or dihydro or tetrahydro fused aryl, unsubstituted or substituted with any substituents being selected from the group consisting of OH, halogen, C1-4 alkyl, C1-4 alkoxy, C3-6 cycloalkyl, OSO2RIV, CN, NO2, OCF3, CF3, CH2CF3, wherein RIV is selected from the group consisting of H, C1-4 alkyl, C3-6 cycloalkyl, C3-6 cycloalkyl;
or R5 is heteroaryl or fused heteroaryl; wherein the hetero-ring contains N, O or S and is aromatic, dihydro or tetrahydro, unsubstituted or substituted with any substituents being selected from the group consisting of OH, OCH3, CH(CH3)2, halogen, C1-4 alkyl, C1-4 alkoxy, C3-6 cycloalkyl, CN, NO2, OCF3, CF3, CH2CF3;
R6 is H, OH or O (forming a ketone); and
A and B are, independently, selected from the group consisting of a bond, CH2, NH, O, S and Cxe2x95x90O, provided that either A or B is selected from CH2 and NH; or A and B together form a bond; or the A-B moiety is represented by CHxe2x95x90CH or Cxe2x89xa1C.
X1 and X5 are independently selected from the group consisting of H, halogen, CN, NO2, C1-4 alkyl, cycloalkyl, CH2-aryl, and CH2-heteroaryl; provided that either X1 or X5 is H; X2, X3 and X4 are selected from the group consisting of H, halogen, Oxe2x80x94C1-4 alkyl, O-aryl. O-heteroaryl, CH2-aryl, CH2-heteroaryl, alkyl, C(O)aryl, C(O)heteroaryl, CH(OH)aryl, and CH(OH)heteroaryl and Jxe2x80x94K
J is a covalent bond, alkylene, O-alkylene or alkenylene of up to 5 carbon atoms, unsubstituted or substituted by a substituent selected from the group consisting of C1-4 alkyl, OH, O(ketone), aryl, heteroaryl, and NRxe2x80x2Rxe2x80x3, wherein Rxe2x80x2 and Rxe2x80x3 are independently selected from the group consisting of H, alkyl, aryl, heteroaryl, C(O)alkyl, C(O)aryl, and C(O)heteroaryl;
K is selected from the group consisting of CO2H, CO2RIV, OH, and CN.
More preferably, R5 is aryl or fused aryl or dihydro or tetrahydro aryl, unsubstituted or substituted with any substituents being selected from the group consisting of OCH3, CH2CH3, halogen, C3-6 heterocycloalkyl, CN, NO2, OCF3, CF3, CH2CF3; or R5 is heteroaryl or fused heteroaryl, wherein the hetero-ring contains N, O or S and is aromatic, dihydro or tetrahydro, unsubstituted or substituted with any substituents being selected from the group consisting of OCH3, halogen, C1-4 alkyl, CN, NO2, OCF3, CF3, CH2CF3;
R6 is H; and
A and B are, independently, selected from the group consisting of a bond, CH2, NH, O, S and Cxe2x95x90O, provided that either A or B is selected from CH2 and NH, or A and B together form a bond.
X1 and X5 are selected from the group consisting of Cl, F, CN, and NO2; provided that either X1 or X5 is H;
X2, X3 and X4 is selected from the group consisting of H,F, Cl, CN, O-aryl, O-heteroaryl, CH2-aryl, CH2-heteroaryl, C(O)aryl, C(O)heteroaryl, CH(OH)aryl, CH(OH)heteroaryl or Jxe2x80x94K
J is a covalent bond, alkylene, alkenylene or O alkylene of up to 5 carbon atoms, unsubstituted or substituted by C1-4 alkyl, aryl, heteroaryl, or NRxe2x80x2Rxe2x80x3, wherein Rxe2x80x2 and Rxe2x80x3 are independently selected from the group consisting of H, alkyl, aryl, heteroaryl, C(O)alkyl, C(O)aryl, and C(O)heteroaryl;
K is CO2RIV;
Most preferably, R5 is phenyl, naphthyl, heteroaryl or fused heteroaryl, wherein the heteroring contains N, O or S, and is aromatic, dihydro or tetrahydro; unsubstituted or substituted with any substituents being selected from the group consisting of halogen, OCH3, CF3, and C1-4alkyl;
R6 is H; and
A and B are, independently, selected from the group consisting of a bond, CH2, O, or A and B together form a bond.
X1 and X5 are independently Cl, CN, or NO2;
provided that either X1 or X5 is H;
X2 or X3 or X4 are H, CN, Cl or Jxe2x80x94K;
J is a covalent bond, alkylene or alkenylene of up to 5 carbon atoms, unsubstituted or substituted by aryl, heteroaryl, or NRxe2x80x2Rxe2x80x3, wherein Rxe2x80x2 and Rxe2x80x3 are selected from the group consisting of H, alkyl, aryl, heteroaryl, C(O)alkyl, C(O)aryl, and C(O)heteroaryl;
K is CO2RIV.
Preferred heteroaryls useful in the present invention include unsubstituted and substituted quinolines, isoquinolines, benzofurans, dihydrobenzofurans, benzothiophenes, dihydrobenzothiophenes and pyridines.
As used herein xe2x80x9ccycloalkylxe2x80x9d refers to optionally substituted 3-7 membered carbocyclic rings wherein any substituents are selected from the group consisting of, F, Cl, Br, I, N(RIV)2, SRIV and O RIV unless otherwise indicated.
As used herein xe2x80x9cheterocycloalkylxe2x80x9d refers to optionally substituted 4, 5, 6 or 7 membered heterocyclic rings containing 1 to 2 heteroatoms selected from N, O, and S.
As used herein, xe2x80x9carylxe2x80x9d refers to an optionally substituted aromatic group with at least one ring having a conjugated pi-electron system, containing up to two conjugated or fused ring systems. Aryl includes carbocyclic aryl, and biaryl groups, all of which may be optionally substituted. Preferred aryl include phenyl and naphthyl. More preferred aryl include phenyl. Preferred substituents are selected from the group consisting of halogen, C1-4 alkyl, OCF3, CF3, OMe, CN, OSO2 R and NO2, wherein R represents C1-4 alkyl or C3-6 cycloalkyl.
As used herein, xe2x80x9cacylxe2x80x9d refers to C1-4 alkylcarbonyl.
As used herein, xe2x80x9calkenylxe2x80x9d refers to an optionally substituted hydrocarbon group containing at least one carbon-carbon double bond and containing up to 5 carbon atoms joined together. The alkenyl hydrocarbon chain may be straight, branched or cyclic. Any substituents are selected from the group consisting of halogen, C1-4 alkyl, OCF3, CF3, OMe, CN, OSO2 R and NO2, wherein R represents C1-4 alkyl or C3-6 cycloalkyl.
As used herein, xe2x80x9calkynylxe2x80x9d refers to an optionally substituted hydrocarbon group containing at least one carbon-carbon triple bond between the carbon atoms and containing up to 5 carbon atoms joined together. The alkynyl hydrocarbon group may be straight-chained, branched or cyclic. Any substituents are selected from the group consisting of halogen, C1-4 alkyl, OCF3, CF3, OMe, CN, OSO2 R and NO2, wherein R represents C1-4 alkyl or C3-6 cycloalkyl.
The compounds of the present invention may contain one or more asymmetric carbon atoms and may exist in racemic and optically active forms. All of these compounds and diastereomers are contemplated to be within the scope of the present invention.
Preferred compounds of the present inventions include:
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carboethoxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carboxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(3-carbethoxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(3-carboxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(2-carbethoxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(2-carboxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(3-carbethoxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(3-carboxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(3-carbethoxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(3-carboxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(2-carbethoxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(2-carboxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(carbethoxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(carboxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(carbethoxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(carboxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carbethoxy-trans-ethylene)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carboxy-trans-ethylene)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3(4-(2-phenyl-2-R,S-methoxycarbonylethyl))phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(4-(2-phenyl-2-R,S-carboxyethyl))phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(3-benzyl-4-methoxycarbonylmethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(3-benzyl-4-methoxycarbonylmethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(3-benzyl-4-carboxymethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(3-benzyl-4-carboxymethyl)phenoxy]-propan-2-ol,
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(4-(3-hydroxy)propyl)phenoxy]-propan-2-ol; (R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(4-(2-hydroxy)ethyl)phenoxy]-propan-2-ol; (R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(4-(2-cyano)ethyl)phenoxy]-propan-2-ol;
(R)-Methyl 2-[4-[3-[2-(4-methoxyphenyl)-1,1-dimethylethyiamino]-2-hydroxypropoxy]benzoylbenzoate;
(R)-2-[4-[3-[2-(4-Methoxyphenyl)-1,1-dimethylethylamino]-2-hydroxypropoxy]benzoylbenzoic acid;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(4-cyanomethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(4-cyano)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(4-methoxycarbonylmethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenylethylamino]-3-[(2-nitro-4-cyano)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(2-nitro-4-(hydroxymethyl))phenoxy ]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(2-nitro-4-methoxycarbonylmethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(2-nitro-4-carboxymethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(4-methoxycarbonyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(4-carboxy)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(2-cyano-4-ethoxycarbonylmethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(2-cyano-4-carboxymethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(4-methoxycarbonylethyl)phenoxy]-propan-2-ol;
N-[2R-hydroxy-3-[[2-nitro-4-[2S-ethoxycarbonyl-2-[methylsulfonyl]amino]phenoxy]propyl]-1,1-dimethyl-2-[4-methoxyphenyl]ethylamine;
N-[2R-hydroxy-3-[[2-nitro-4-[2S-methoxycarbonyl-2-[phthalimido]phenoxy]propyl]-1,1-dimethyl-2-[naphthyl]ethylamine;
N-[2R-hydroxy-3-[[2-nitro-4-[2S-carboxy-2-[[[2-carboxy]phenyl]carbonyl]amino]ethyl]phenoxy]propyl]-1,1-dimethyl-2-[naphthyl]ethylamine;
N-[2R-hydroxy-3-[[2-nitro-4-[2S-methoxycarbonyl-2-[[[2-carboxy]phenyl]carbonyl]amino]ethyl]phenoxy]propyl]-1,1-dimethyl-2-[naphthyl]ethylamine;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(3-(2-aminophenoxy)-4-methoxycarbonyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(3-(2-aminophenoxy)-4-carboxy)phenoxy]-propan-2-ol;
and pharmaceutically acceptable salts and complexes thereof.
More preferred compounds of the present invention include:
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carboethoxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carboxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(3-carbethoxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(3-carboxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(2-carbethoxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine; (R)-N-[2-Hydroxy-3-(2-cyano-5-(2-carboxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(3-carbethoxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(3-carboxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(3-carbethoxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(3-carboxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(2-carbethoxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(2-carboxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(carbethoxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(carboxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(carbethoxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(carboxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carbethoxy-trans-ethylene)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carboxy-trans-ethylene)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(3-(2-aminophenoxy)4-methoxycarbonyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3(4-(2-phenyl-2-R,S-methoxycarbonylethyl))phenoxy]-propan-2-ol,
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(3-benzyl-4-methoxycarbonylmethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(3-benzyl-4-methoxycarbonylmethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(3-benzyl-4-carboxymethyl)phenoxy]-propan-2-ol;
(R)-Methyl 2-[4-[3-[2-(4-methoxyphenyl)-1,1-dimethylethylamino]-2-hydroxypropoxy]benzoylbenzoate;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(2-cyano-4-ethoxycarbonylmethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(4-methoxyphenyl)ethylamino]-3-[(2-nitro-4-methoxycarbonylmethyl)phenoxy]-propan-2-ol;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(4-methoxycarbonyl)phenoxy ]-propan-2-ol; N-[2R-hydroxy-3-[[2-nitro-4-[2S-ethoxycarbonyl-2-[methylsulfonyl]amino]phenoxy]propyl]-1,1-dimethyl-2-[4-methoxyphenyl]ethylamine; N-[2R-hydroxy-3-[[2-nitro-4-[2S-methoxycarbonyl-2-[phthalimido]phenoxy]propyl]-1,1-dimethyl-2-[naphthyl]ethylamine;
N-[2R-hydroxy-3-[[2-nitro-4-[2S-methoxycarbonyl-2-[[[2-carboxy]phenyl]carbonyllamino]ethyl]phenoxy]propyl]-1,1-dimethyl-2-[naphthyl]ethylamine; and
pharmaceutically acceptable salts and complexes thereof.
The most preferred compounds useful in the present invention include:
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carboethoxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carboxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(3-carbethoxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(3-carboxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(2-carbethoxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(2-carboxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(3-carbethoxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(3-carboxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine:
(R)-N-[2-Hydroxy-3-(2-cyano-3-(3-carbethoxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(3-carboxypropyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(2-carbethoxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-3-(2-carboxyethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(carbethoxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(carboxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(carbethoxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-5-(carboxymethyl)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carbethoxy-trans-ethylene)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-N-[2-Hydroxy-3-(2-cyano-4-(2-carboxy-trans-ethylene)phenoxy)propyl]-1,1-dimethyl-2-(2-naphthyl)ethylamine;
(R)-1-[1,1-dimethyl-2-(2-naphthyl)ethylamino]-3-[(3-(2-aminophenoxy)-4-methoxycarbonyl)phenoxy]-propan-2-ol; and
and pharmaceutically acceptable salts and complexes thereof.
Pharmaceutically acceptable salts are non-toxic salts in the amounts and concentrations at which they are administered.
Pharmaceutically acceptable salts include acid addition salts such as those containing sulfate, hydrochloride, fumarate, maleate, phosphate, sulfamate, acetate, citrate, lactate, tartrate, methanesulfonate, ethanesulfonate, benzenesulfonate, p-toluenesulfonate, cyclohexylsulfamate and quinate. A preferred salt is a hydrochloride. Pharmaceutically acceptable salts can be obtained from acids such as hydrochloric acid, maleic acid, sulfuric acid, phosphoric acid, sulfamic acid, acetic acid, citric acid, lactic acid, tartaric acid, malonic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, cyclohexylsulfamic acid, fumaric acid, and quinic acid.
Pharmaceutically acceptable salts also include basic addition salts such as those containing benzathine, chloroprocaine, choline, diethanolamine, ethylenediamine, meglumine, procaine, aluminum, calcium, lithium, magnesium, potassium, sodium, ammonium, alkylamine, and zinc, when acidic functional groups, such as carboxylic acid or phenol are present.
The present invention provides compounds of Formula (I) above which can be prepared using standard techniques. An overall strategy for preparing preferred compounds described herein can be carried out as described in this section. The examples which follow illustrate the synthesis of specific compounds. Using the protocols described herein as a model, one of ordinary skill in the art can readily produce other compounds of the present invention.
All reagents and solvents were obtained from commercial vendors. Starting materials (e.g., amines and epoxides) were synthesized using standard techniques and procedures. 
A general procedure used to synthesize many of the compounds can be carried out as described in Scheme 1: a solution of aryl alcohol in acetone was treated with an appropriate base such as K2CO3, heated for 15 min. R-glycidyl nosylate was added and the reaction continued overnight to give the corresponding glycidyl ether. In the case of an alkyl alcohol (e.g., Y3 is C1-4 alkylene-O), a stronger base, e.g. NaH in DMF was used. This method can also be used for aryl alcohols. A solution of the substituted glycidyl ether and excess amine (typically 1,1-dimethyl-2-(4-methyloxyphenyl)ethylamine) in absolute ethanol, acetonitrile, THF or any other similar solvent in the presence of a suitable catalyst such as LiClO4 is stirred overnight at reflux. The product is purified by normal phase chromatography. Hydrochloride salts are prepared by treatment of the corresponding free base with HCl either in gas phase or 4M dioxane solution, or any other standard method. A method for preparing methyl 2-(2-benzyl-4-hydroxy)phenylacetates is outlined in Scheme 2. Grignard addition followed by dehydration and oxidative cleavage of the resulting double bond yields the benzophenone derivative which is deoxygenated and demethylated to give the aryl alcohol acid and its corresponding ester. A method for preparing 1-(2-aminophenoxy)-2-methoxycarbonyl-5-hydroxy-benzenes is outlined in Scheme 3. Displacement of the aryl fluoride gave the biphenyl ether. Reduction of the nitro group followed by cleavage of the methyl ether gave the desired aryl alcohol. Schemes 4-9 outlines the general synthesis of the corresponding phenol substituted with the different propionic and butiric acid/esters side chains, with appropriate manipulation and protection of any chemical functionality, synthesis of the remaining compounds of Formula (I) is accomplished by methods analogous to those above and to those described in the Experimental section.
In order to use a compound of Formula (I) or a pharmaceutically acceptable salt thereof for the treatment of humans and other mammals, it is normally formulated in accordance with standard pharmaceutical practice as a pharmaceutical composition.
The calcilytic compounds can be administered by different routes including intravenous, intraperitoneal, subcutaneous, intramuscular, oral, topical (transdermal), or transmucosal administration. For systemic administration, oral administration is preferred. For oral administration, for example, the compounds can be formulated into conventional oral dosage forms such as capsules, tablets, and liquid preparations such as syrups. elixirs, and concentrated drops.
Alternatively, injection (parenteral administration) may be used, e.g., intramuscular, intravenous, intraperitoneal, and subcutaneous. For injection, the compounds of the invention are formulated in liquid solutions, preferably, in physiologically compatible buffers or solutions, such as saline solution, Hank""s solution, or Ringer""s solution. In addition, the compounds may be formulated in solid form and redissolved or suspended immediately prior to use. Lyophilized forms can also be produced.
Systemic administration can also be by transmucosal or transdermal means. For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art, and include, for example, for transmucosal administration, bile salts and fusidic acid derivatives. In addition, detergents may be used to facilitate permeation. Transmucosal administration, for example, may be through nasal sprays, rectal suppositories, or vaginal suppositories.
For topical administration, the compounds of the invention can be formulated into ointments, salves, gels, or creams, as is generally known in the art.
The amounts of various calcilytic compounds to be administered can be determined by standard procedures taking into account factors such as the compound IC50, EC50, the biological half-life of the compound, the age, size and weight of the patient, and the disease or disorder associated with the patient. The importance of these and other factors to be considered are known to those of ordinary skill in the art.
Amounts administered also depend on the routes of administration and the degree of oral bioavailability. For example, for compounds with low oral bioavailability, relatively higher doses will have to be administered.
Preferably the composition is in unit dosage form. For oral application, for example, a tablet, or capsule may be administered, for nasal application, a metered aerosol dose may be administered, for transdermal application, a topical formulation or patch may be administered and for transmucosal delivery, a buccal patch may be administered. In each case, dosing is such that the patient may administer a single dose.
Each dosage unit for oral administration contains suitably from 0.01 to 500 mg/Kg, and preferably from 0.1 to 50 mg/Kg, of a compound of Formula (I) or a pharmaceutically acceptable salt thereof, calculated as the free base. The daily dosage for parenteral, nasal, oral inhalation, transmucosal or transdermal routes contains suitably from 0.01 mg to 100 mg/Kg, of a compound of Formula(I). A topical formulation contains suitably 0.01 to 5.0% of a compound of Formula (I). The active ingredient may be administered, for example, from 1 to 6 times per day, preferably once, sufficient to exhibit the desired activity, as is readily apparent to one skilled in the art.
As used herein, xe2x80x9ctreatmentxe2x80x9d of a disease includes, but is not limited to prevention, retardation and prophylaxis of the disease.
Diseases and disorders which might be treated or prevented, based upon the affected cells, include bone and mineral-related diseases or disorders; hypoparathyroidism; those of the central nervous system such as seizures, stroke, head trauma, spinal cord injury, hypoxia-induced nerve cell damage, such as occurs in cardiac arrest or neonatal distress, epilepsy, neurodegenerative diseases such as Alzheimer""s disease, Huntington""s disease and Parkinson""s disease, dementia, muscle tension, depression, anxiety, panic disorder, obsessive-compulsive disorder, post-traumatic stress disorder, schizophrenia, neuroleptic malignant syndrome, and Tourette""s syndrome; diseases involving excess water reabsorption by the kidney, such as syndrome of inappropriate ADH secretion (SIADH). cirrhosis, congestive heart failure, and nephrosis; hypertension; preventing and/or decreasing renal toxicity from cationic antibiotics (e.g., aminoglycoside antibiotics); gut motility disorders such as diarrhea and spastic colon; GI ulcer diseases; GI diseases with excessive calcium absorption such as sarcoidosis; autoimmune diseases and organ transplant rejection: squamous cell carcinoma; and pancreatitis.
In a preferred embodiment of the present invention, the present compounds are used to increase serum parathyroid hormone (xe2x80x9cPTHxe2x80x9d) levels. Increasing serum PTH levels can be helpful in treating diseases such as hypoparathyroidism, osteosarcoma, periodontal disease, fracture, osteoarthritis, rheumatoid arthritis, Paget""s disease, humoral hypercalcemia malignancy and osteoporosis.
Another aspect of the present invention describes a method of treating a patient comprising administering to the patient an amount of a present compound sufficient to increase the serum PTH level. Preferably, the method is carried out by administering an amount of the compound effective to cause an increase in duration and/or quantity of serum PTH level sufficient to have a therapeutic effect.
In various embodiments, the compound administered to a patient causes an increase in serum PTH having a duration of up to one hour, about one to about twenty-four hours, about one to about twelve hours, about one to about six hours, about one to about five hours, about one to about four hours, about two to about five hours, about two to about four hours, or about three to about six hours.
In an altemattive embodimenf of the present invention, the compound administered to a patient causes an increase in serum PTH having a duration of more than about twenty four hours provided that it is co-administered with an anti resorptive agent.
In additional different embodiments, the compound administered to a patient causes an increase in serum PTH of up to two fold, two to five fold, five to ten fold, and at least 10 fold, greater than peak serum PMN in the patient. The peak serum level is measured with respect to a patient not undergoing treatment.
Composition of Formula (I) and their pharmaceutically acceptable salts which are active when given orally can be formulated as syrups, tablets, capsules and lozenges. A syrup formulation will generally consist of a suspension or solution of the compound or salt in a liquid carrier for example, ethanol, peanut oil olive oil, glycerine or water with a flavoring or coloring agent. Where the composition is in the form of a tablet, any pharmaceutical carrier routinely used for preparing solid formulations may be used. Examples of such carriers include magnesium stearate, terra alba, talc, gelatin, acacia, stearic acid, starch, lactose and sucrose. Where the composition is in the form of a capsule, any routine encapsulation is suitable, for example using the aforementioned carriers in a hard gelatin capsule shell. Where the composition is in the form of a soft gelatin shell capsule any pharmaceutical carrier routinely used for preparing dispersions or suspensions may be considered, for example aqueous gums, celluloses, silicates or oils, and are incorporated in a soft gelatin capsule shell.
Typical parenteral compositions consist of a solution or suspension of a compound or salt in a sterile aqueous or non-aqueous carrier optionally containing a parenterally acceptable oil, for example polyethylene glycol, polyvinylpyrrolidone, lecithin, arachis oil or sesame oil.
Typical compositions for inhalation are in the form of a solution, suspension or emulsion that may be administered as a dry powder or in the form of an aerosol using a conventional propellant such as dichlorodifluoromethane or trichlorofluoromethane.
A typical suppository formulation comprises a compound of Formula (I) or a pharmaceutically acceptable salt thereof which is active when administered in this way, with a binding and/or lubricating agent, for example polymeric glycols, gelatins, cocoa-butter or other low melting vegetable waxes or fats or their synthetic analogs.
Typical dermal and transdermal formulations comprise a conventional aqueous or non-aqueous vehicle, for example a cream, ointment, lotion or paste or are in the form of a medicated plaster, patch or membrane.
Preferably the composition is in unit dosage form, for example a tablet, capsule or metered aerosol dose, so that the patient may administer a single dose.
No unacceptable toxological effects are expected when compounds of the present invention are administered in accordance with the present invention.
The biological activity of the compounds of Formula (I) are demonstrated by the following tests:
(I) Calcium Receptor Inhibitor Assay
Calcilytic activity was measured by determining the IC50 of the test compound for blocking increases of intracellular Ca2+ elicited by extracellular Ca2+ in HEK 293 4.0-7 cells stably expressing the human calcium receptor. HEK 293 4.0-7 cells were constructed as described by Rogers et al., J. Bone Miner. Res. 10 Suppl. 1:S483, 1995 (hereby incorporated by reference herein). Intracellular Ca2+ increases were elicited by increasing extracellular Ca2+ from 1 to 1.75 mM. Intracellular Ca2+ was measured using fluo-3, a fluorescent calcium indicator.
The procedure was as follows:
1. Cells were maintained in T-150 flasks in selection media (DMEM supplemented with 10% fetal bovine serum and 200 ug/mL hygromycin B), under 5% CO2:95% air at 37xc2x0 C. and were grown up to 90% confluency.
2. The medium was decanted and the cell monolayer was washed twice with phosphate-buffered saline (PBS) kept at 37xc2x0 C. After the second wash, 6 mL of 0.02% EDTA in PBS was added and incubated for 4 minutes at 37xc2x0 C. Following the incubation, cells were dispersed by gentle agitation.
3. Cells from 2 or 3 flasks were pooled and pelleted (100xc3x97g). The cellular pellet was resuspended in 10-15 mL of SPF-PCB+ and pelleted again by centrifugation. This washing was done twice.
Sulfate- and phosphate-free parathyroid cell buffer (SPF-PCB) contains 20 mM Na-Hepes, pH 7.4, 126 mM NaCl, 5 mM KCl, and 1 mM MgCl2. SPF-PCB was made up and stored at 4xc2x0 C. On the day of use, SPF-PCB was supplemented with 1 mg/mL of D-glucose and 1 mM CaCl2 and then split into two fractions. To one fraction, bovine serum albumin (BSA; fraction V, ICN) was added at 5 mg/mL (SPF-PCB+). This buffer was used for washing, loading and maintaining the cells. The BSA-free fraction was used for diluting the cells in the cuvette for measurements of fluorescence.
4. The pellet was resuspended in 10 mL of SPF-PCB+ containing 2.2 uM fluo-3 (Molecular Probes) and incubated at room temperature for 35 minutes.
5. Following the incubation period, the cells were pelleted by centrifugation. The resulting pellet was washed with SPF-PCB+. After this washing, cells were resuspended in SPF-PCB+ at a density of 1-2xc3x97106 cells/mL.
6. For recording fluorescent signals, 300 uL of cell suspension were diluted in 1.2 mL of SPF buffer containing 1 mM CaCl2 and 1 mg/mL of D-glucose. Measurements of fluorescence were performed at 37xc2x0 C. with constant stirring using a spectrofluorimeter. Excitation and emission wavelengths were measured at 485 and 535 nm, respectively. To calibrate fluorescence signals, digitonin (5 mg/mL in ethanol) was added to obtain Fmax, and the apparent Fmin was determined by adding Tris-EGTA (2.5 M Tris-Base, 0.3 M EGTA). The concentration of intracellular calcium was calculated using the following equation:
Intracellular calcium=(Fxe2x88x92Fmin/Fmax)xc3x97Kd; where Kd=400 nM.
7. To determine the potential calcilytic activity of test compounds, cells were incubated with test compound (or vehicle as a control) for 90 seconds before increasing the concentration of extracellular Ca2+ from 1 to 2 mM. Calcilytic compounds were detected by their ability to block, in a concentration-dependent manner, increases in the concentration of intracellular Ca2+ elicited by extracellular Ca2+.
In general, those compounds having lower IC50 values in the Calcium Receptor Inhibitor Assay are more preferred compounds. Compounds having an IC50 greater than 50 uM were considered to be inactive. Preferred compounds are those having an IC50 of 10 uM or lower, more preferred compounds have an IC50 of 1 uM, and most preferred compounds have an IC50 of 0.1 uM or lower.
(II) Calcium Receptor Binding Assay
HEK 293 4.0-7 cells stably transfected with the Human Parathyroid Calcium Receptor(xe2x80x9cHuPCaRxe2x80x9d) were scaled up in T180 tissue culture flasks. Plasma membrane is obtained by polytron homogenization or glass douncing in buffer (50 mM Tris-HCl pH 7.4, 1 mM EDTA, 3 mM MgCl2) in the presence of a protease inhibitor cocktail containing 1 uM Leupeptin, 0.04 uM Pepstatin, and 1 mM PMSF. Aliquoted membrane was snap frozen and stored at xe2x88x9280xc2x0 C. 3H labeled compound was radiolabeled to a radiospecific activity of 44Ci/mmole and was aliquoted and stored in liquid nitrogen for radiochemical stability.
A typical reaction mixture contains 2 nM 3H compound ((R,R)-N-4xe2x80x2-Methoxy-t-3-3xe2x80x2-methyl-1xe2x80x2-ethylphenyl-1-(1-naphthyl)ethylamine), or 3H compound (R)-N-[2-Hydroxy-3-(3-chloro-2-cyanophenoxy)propyl]-1,1-dimethyl-2-(4-methoxyphenyl)ethylamine 4-10 ug membrane in homogenization buffer containing 0.1% gelatin and 10% EtOH in a reaction volume of 0.5 mL. Incubation is performed in 12xc3x9775 polyethylene tubes in an ice water bath. To each tube 25 uL of test sample in 100% EtOH is added, followed by 400 uL of cold incubation buffer, and 25 uL of 40 nM 3H-compound in 100% EtOH for a final concentration of 2 nM. The binding reaction is initiated by the addition of 50 uL of 80-200 ug/mL HEK 293 4.0-7 membrane diluted in incubation buffer, and allowed to incubate at 4xc2x0 C. for 30 min. Wash buffer is 50 mM Tris-HCl containing 0.1% PEI. Nonspecific binding is determined by the addition of 100-fold excess of unlabeled homologous ligand, and is generally 20% of total binding. The binding reaction is terminated by rapid filtration onto 1% PEI pretreated GF/C filters using a Brandel Harvestor. Filters are placed in scintillation fluid and radioactivity assessed by liquid scintillation counting.